Apparatus and methods for a mask inverter

ABSTRACT

In some embodiments, apparatus and methods are provided for improved handling of lithography masks including a mask inverter that includes a first contact pad dedicated to inverting masks that have not been cleaned; a second contact pad dedicated to inverting masks that have been cleaned; an actuator coupled to the first and second contact pads and operable to invert the first and second contact pads; and a controller coupled to the actuator and operative to control the actuator. Numerous other aspects are provided.

This application is a divisional of and claims priority to U.S. patent application Ser. No. 14/499,122 filed Sep. 27, 2014, and titled “APPARATUS AND METHODS FOR A MASK INVERTER” (Attorney Docket No. 20470-02), which claims priority to U.S. Provisional Patent Application No. 61/884,048, filed on Sep. 28, 2013, and entitled “APPARATUS AND METHODS FOR A MASK INVERTER,” (Attorney Docket No. 20470-02/L), and U.S. Provisional Patent Application No. 61/884,049, also filed on Sep. 28, 2013, and entitled “METHODS AND SYSTEMS FOR IMPROVED MASK PROCESSING,” (Attorney Docket No. 20470/L). All of the above applications are hereby incorporated by reference herein in their entirety.

FIELD

The present application relates to lithography masks, and more specifically to apparatus and methods for a mask inverter.

BACKGROUND

Particle contamination can be a significant problem in semiconductor manufacturing. A photomask is typically protected from contaminating particles by a pellicle, a thin transparent film stretched over a frame that is glued over one side of the photomask. The pellicle is far enough away from the mask patterns so that moderate-to-small sized particles that land on the pellicle will be too far out of focus to print. Although they are designed to keep particles away, pellicles become a part of the imaging system and their optical properties effect the lithography and are taken into account.

Conventionally, a pellicle can be used to protect and prevent contamination of the patterned side of ultraviolet (e.g., using 193 nm argon fluorine exciplex lasers) optical lithography masks. However, extreme ultraviolet (EUV) lithography does not allow the use of a pellicle due to the optical effects of the pellicle. However, if the bare mask is not handled properly, there is a risk of contamination.

Thus, EUV masks (without the protection of a pellicle) are typically only handled in a vacuum. For example, a mask carrier with a nested inner carrier that conforms to the SEMI E152 standard provides double isolation of the bare mask for contamination control, with the assumption that the inner carrier will only be opened in a vacuum. However, an inner carrier opener in a vacuum presents significant cost and complexity. Thus, what is needed are apparatus and methods that facilitate handling such as mask inversion without requiring nested carriers and vacuum isolation.

SUMMARY

In some embodiments, the invention provides an apparatus for inverting a mask. The apparatus includes a first contact pad dedicated to inverting masks that have not been cleaned; a second contact pad dedicated to inverting masks that have been cleaned; an actuator coupled to the first and second contact pads and operable to invert the first and second contact pads; and a controller coupled to the actuator and operative to control the actuator.

In other embodiments, the invention provides a method of handling a mask. The method includes loading a mask onto a first contact pad of a mask inverter using a first end effector; inverting the mask using the first contact pad; unloading the mask from the mask inverter using the first end effector; cleaning the mask; loading the mask onto a second contact pad of the mask inverter using a second end effector; inverting the mask using the second contact pad; and unloading the mask from the mask inverter using the second end effector.

In yet other embodiments, the invention provides a system for handling masks. The system includes a first load port; an atmospheric dual blade robot operable to access a first carrier in the first load port; a mask inverter including two contact pads and disposed to receive masks from the atmospheric dual blade robot; and a mask cleaning system disposed to receive masks from the atmospheric dual blade robot.

Numerous other aspects are provided in accordance with these and other aspects of the invention. Other features and aspects of the present invention will become more fully apparent from the following detailed description, the appended claims and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic depiction of an example system for improved mask handling according to embodiments provided herein.

FIG. 2 is a schematic depiction of an apparatus for inverting a mask according to embodiments provided herein.

FIG. 3 is a flow chart depicting an example method for improved mask handling according to embodiments provided herein.

DETAILED DESCRIPTION

Embodiments provided herein provide apparatus and methods for minimizing or reducing the risk of contamination while handling bare EUV masks, particularly at atmospheric conditions. The apparatus includes a mask inverter or “flipper” that has two sets of contact pads so that a first contact pad can be dedicated to inverting “uncleaned” (e.g., versus post-cleaned) masks while a second contact pad can be dedicated to inverting cleaned masks within a wet clean tool to prevent re-contamination after cleaning. Thus, cleaned masks are not handled with contact pads that have previously handled masks before the masks were cleaned and masks that have not yet been cleaned are not handled with contact pads dedicated to only handling masks that have been cleaned.

Embodiments of the present invention provide advantages both in terms of reduced cost and complexity as well as a reduction of contamination of EUV masks which in turn increases yield and output from electronic device manufacturing facilities. In addition to EUV optical mask handling, the apparatus and methods provided herein can be applied to handling other masks, reticles, and electric device substrates to reduce particle contamination.

FIG. 1 is a schematic diagram of a first example system 100 provided herein. A first load port 102 is coupled to the factory interface of a mask processing tool such as a mask cleaning tool. The load port 102 is disposed so that an atmospheric dual blade factory interface robot 104 can remove the mask to be cleaned from a carrier placed in the load port 102. Thus, the carrier is opened into a non-vacuum factory interface. The robot 104 includes two end effectors. The first end effector is dedicated to only handling masks that have not yet been cleaned. The second end effector is dedicated to only handing masks that have already been cleaned. Thus, contamination of a mask that has been cleaned is avoided by not handling the clean mask with an end effector that has handled unclean masks.

The inventors of the present application have determined that before a mask is cleaned, potentially contaminating particles are transferable from the unclean mask to the end effector when the mask is moved from the load port. Further, these particles can then be transferred again from the end effector to a subsequently handled mask. If the mask has already undergone a cleaning process, the particle transfer back to the mask from the end effector can contaminate the clean mask. Thus, one or more embodiments provided herein avoid this potential for contamination by only handing a clean mask with end effectors that have not handled unclean masks.

The system 100 further includes a mask inverter 106. In some embodiments, the mask inverter 106 can be disposed at a load port location as shown in FIG. 1. In some embodiments, the mask inverter can be located at any practicable location such as alongside the factory interface or between the tool and the factory interface within the system 100. As will be discussed in more detail below, the mask inverter 106 includes two different contact pads. The first contact pad is dedicated to only handling and inverting masks that have not yet been cleaned. The second contact pad is dedicated to only handing masks that have already been cleaned. Thus, contamination of a mask that has been cleaned is avoided by not handling the clean mask with a contact pad that has held unclean masks.

As with end effectors, the inventors of the present application have determined that before a mask is cleaned, potentially contaminating particles are transferable from the unclean mask to the contact pads of the inverter 106 when the mask is held by the inverter 106. Further, these particles can then be transferred again from the contact pad to a subsequently held mask. If the mask has already undergone a cleaning process, the particle transfer back to the mask from the contact pad can contaminate the clean mask. Thus, one or more embodiments provided herein avoid this potential for contamination by only holding a clean mask with contact pads that have not held unclean masks.

The system 100 can further include a dry clean tool 108 such as an etch process tool for, e.g., removing oxidation from the mask before the mask under goes wet clean processing. An example of such a tool is the Axiom™ strip chamber manufactured by Applied Materials, Inc. of Santa Clara, Calif.

In some embodiments, the system 100 can include buffer stations 110, 116 within an intermediate module between the factory interface and an atmospheric process module that includes a plurality of mask wet clean chambers 112. The buffer stations 110, 116 provide a location for the factory interface robot 104 and an atmospheric dual blade process robot 114 to facilitate mask handoff. One of the buffer stations 110 is dedicated to holding unclean masks while the other buffer station 116 is dedicated to holding cleaned masks. Thus, contamination of a mask that has been cleaned is avoided by not storing the clean mask on a buffer station that has held unclean masks.

As with end effectors and contact pads, the inventors of the present application have determined that before a mask is cleaned, potentially contaminating particles are transferable from the mask to a buffer station when the unclean mask is held in the buffer station. Further, these particles can then be transferred again from the buffer station to a subsequently held mask. If the mask has already undergone a cleaning process, the particle transfer back to the mask from the buffer station can contaminate the clean mask. Thus, one or more embodiments provided herein avoid this potential for contamination by only holding a clean mask in a buffer station that has not held unclean masks.

In some embodiments, the system 100 can include a second load port 118 coupled to the factory interface. The second load port 118 is disposed so that the atmospheric dual blade factory interface robot 104 can load a cleaned mask into a carrier placed in the load port 118.

In some embodiments, a second load port is not used and instead, cleaned masks exit the system via the first load port 102. In such embodiments, a first carrier that brings the unclean mask to the system 100 is replaced with a second carrier to remove the cleaned mask from the system 100. In other words, after a mask to be cleaned has been removed from the carrier within which the unclean mask arrived, the carrier is removed from the load port 102 and a new carrier that has not stored unclean masks is placed on the load port 102 to receive the clean mask. Therefore, some of the carriers used by the system are dedicated to holding only unclean masks while other carriers are dedicated to holding only cleaned masks. Thus, contamination of a mask that has been cleaned is avoided by not storing the cleaned mask in a carrier that has held unclean masks.

As with end effectors, contact pads, and buffer stations, the inventors of the present application have determined that before a mask is cleaned, potentially contaminating particles are transferable from the mask to a carrier when the unclean mask is held in the carrier. Further, these particles can then be transferred again from the carrier to a subsequently held mask. If the mask has already undergone a cleaning process, the particle transfer back to the mask from the carrier can contaminate the clean mask. Thus, one or more embodiments provided herein avoid this potential for contamination by only holding a clean mask in a carrier that has not held unclean masks.

Finally, the system 100 includes a controller 120 (e.g., a programmed processor) adapted to execute instructions to implement the functions and methods described herein. The controller 120 can be implemented as a single processor operatively coupled to each of the components to control their operation or the controller 120 can be implemented as multiple processors, one for each component, in communication with each other and/or with an electronic device manufacturing facility automation system.

FIG. 2 is a schematic diagram of an example embodiment of a mask inverter 200 (e.g., mask inverter 106 in FIG. 1) provided herein. The mask inverter 200 includes a first contact pad 202 for holding and inverting masks that have not yet been cleaned. The mask inverter 200 also includes a second contact pad 204 for holding and inverting masks that have been cleaned. Note that the relative positions of the contact pads 202, 204 depicted in FIG. 2 are merely examples provided for illustrative purposes and the relative positions can be any practicable positions. The contact pads 202, 204 are both operable to each securely hold a mask while the mask is inverted. Thus, in some embodiments, an electrostatic check can be used to hold a mask to the contact pad 202, 204. In other embodiments, mechanical chucks that apply pressure to the sides or edges of the mask may be used. In yet other embodiments, a vacuum chuck may be used. Further, the contact pads 202, 204 can include sensors to detect the presence of a mask and, in some embodiments, the orientation of the mask. In some embodiments, the sensors can be configured to detect misalignment of a mask placed on the contact pads or other fault conditions.

The mask inverter 200 further includes one or more actuators 206 that are operable to invert the contact pads 202, 204. In some embodiments, the actuators 206 can include a single mechanism that inverts both contact pads 202, 204 concurrently. In some embodiments, the actuators 206 can include two or more mechanisms operable to invert the contact pads 202, 204 independently of each other.

Finally, the mask inverter 200 can include a controller 208 (e.g., a programmed processor) coupled to the actuators 206 (and contact pad sensors) and adapted to execute instructions to help implement the functions and methods described herein. For example, in operation, the controller 208 can receive feedback from the sensors that a mask is present on one of the contact pads. In response, the controller 208 can control the contact pad to activate an electro-static chuck and control the actuators 206 to invert the contact pad holding the mask.

In some embodiments, the controller 208 can be implemented as an embedded processor operative to monitor and control the components of the mask inverter 200. In some embodiments, the controller 208 can be implemented remote from the mask inverter 200 and be adapted to monitor and control the mask inverter 200 via remote signaling to and from an electronic device manufacturing facility automation system.

FIG. 3 is a flowchart of an example method 300 provided herein. A mask to be cleaned is loaded onto a first contact pad of a mask inverter using a first end effector of an atmospheric dual blade factory interface robot (302). The mask is secured to the first contact pad of the inverter and then inverted (304). The mask is then unloaded from the first contact pad using the first end effector (306).

The mask is then cleaned (308). Cleaning the mask can include putting the mask through a dry clean process chamber and/or a wet clean process chamber. End effectors and buffer stations used to handle the mask can include end effectors and buffer stations dedicated to handling the mask before the cleaning process and separate end effectors and buffer stations dedicated to handling the mask after the cleaning process.

After the mask has been cleaned, the mask is transferred to a second contact pad of the inverter (310) The mask is secured to the second contact pad and then inverted (312). A second end effector that has not handled unclean masks is then used to transfer the mask from the inverter (314).

The foregoing description discloses only example embodiments of the invention. Modifications of the above disclosed apparatus and methods which fall within the scope of the invention will be readily apparent to those of ordinary skill in the art.

Accordingly, while the present invention has been disclosed in connection with example embodiments thereof, it should be understood that other embodiments may fall within the spirit and scope of the invention, as defined by the following claims. 

The invention claimed is:
 1. A system for handling masks comprising: a first load port; an atmospheric dual blade robot operable to access a first carrier in the first load port; a mask inverter including two contact pads and disposed to receive masks from the atmospheric dual blade robot; and a mask cleaning system disposed to receive masks from the atmospheric dual blade robot.
 2. The system of claim 1 wherein the system for handling masks is operative to handle masks that have not been cleaned with a first set of end effectors and contact pads, and wherein the system for handling masks is operative to handle masks that have been cleaned with a second set of end effectors and contact pads.
 3. The system of claim 1 wherein the mask inverter includes: a first contact pad dedicated to inverting masks that have not been cleaned; a second contact pad dedicated to inverting masks that have been cleaned; an actuator coupled to the first and second contact pads and operable to invert the first and second contact pads; and a controller coupled to the actuator and operative to control the actuator.
 4. The system of claim 3 wherein the first and second contact pads each include a chuck to hold a mask.
 5. The system of claim 4 wherein the chucks are electro-static chucks.
 6. The system of claim 3 wherein the first and second contact pads each include a sensor for detecting a mask on the contact pads.
 7. The system of claim 6 wherein the sensors are coupled to the controller and operable to detect an orientation of a mask on the contact pads.
 8. The system of claim 6 wherein the sensors are coupled to the controller and operable to detect misalignment of a mask on the contact pads.
 9. The system of claim 3 wherein the actuator is operable to invert the contact pads independently of each other.
 10. A method of handling masks comprising: loading a mask onto a first contact pad of a mask inverter using a first end effector; inverting the mask using the first contact pad; unloading the mask from the mask inverter using the first end effector; cleaning the mask; loading the mask onto a second contact pad of the mask inverter using a second end effector; inverting the mask using the second contact pad; and unloading the mask from the mask inverter using the second end effector.
 11. The method of claim 10 wherein loading the mask onto a first contact pad includes securing the mask to the first contact pad via a first chuck, and wherein loading the mask onto a second contact pad includes securing the mask to the second contact pad via a second chuck.
 12. The method of claim 10 wherein loading the mask onto a first contact pad includes detecting the mask on the first contact pad using a first sensor, and wherein loading the mask onto a second contact pad includes detecting the mask on the second contact pad using a second sensor.
 13. The method of claim 10 wherein loading the mask onto a first contact pad includes transferring the mask from a first load port, and wherein unloading the mask from the mask inverter includes transferring the mask from the second contact pad to a second load port. 